So I have a lot of problems in my 1996 f150 with the 300 in it. Ran like a champ till January 27th. Been working on it ever since. First problem was the fuel tanks. 10 psi on front, 8 psi on the rear, so I replaced them both. All last year the truck ran very slightly under powered after replacing the e4od trans which I had rebuilt and worked fine. It wasn't too bad, so I ignored it. Back then it was running these codes: 1151, 0174, and (intermittently) 0403. In January I had to replace both pumps, the front which had gone out in the past summer. Once that was done, the truck ran with psi at 50+. Ran awful. It starts just fine for the most part, but as it warms up, the engine starts ticking like a diesel engine. I thought that the EGR might have issues. Tapping on the valve made the engine run smoother, but still had the clatter. The truck cannot go over 40 mph at all, can barely accelerate. I have spark, a good hot half inch on all cylinders. Have not checked the plugs for fuel wetness. Tore the upper manifold apart to clean the throttle body and EGR valve with carb cleaner, and the IAC with contact cleaner. The EGR is by no means stuck. I've suspected the fuel regulator, but have no way of testing it. I'm gonna go out and clean the injectors while I've got the upper manifold off. I'm running codes 1151, 0155, 0135, 0141, 1131. The O2 sensors I replaced 17k miles ago. Any ideas?

 

The clatter is probably a cracked or warped exhaust manifold. Any leaks upstream of the O2 sensors will trigger lean codes. Fix the exhaust leak, most of your issues will be resolved. Except for the O2 sensor heater circuit codes. That's another problem.

 

Warped manifold? Aarrgg!

Then again, I can almost understand why, since I forgot to put on my radiator cap after adding radiator stop leak. Bad idea on all parts. (what can I say. my linkedin says school of hard knocks!) The truck boiled out all the coolant, overheated and stalled. I got that diesel tick during that experience. But I'm curious why it only started just recently? I'd think I could have sensed something sooner than I did.

And, I've heard thoughts of bad valve rockers or pushrods. I've got the upper manifold off to clean injectors, egr and throttle body, so what should I check under the valve cover? Thanks a bunch.

 

You overheated the engine enough to stall? There could be more damaged than just a warped/cracked exhaust manifold. The clatter could also be rod or main bearing related.

Take a good look at the intake manifold and mounting surfaces for signs of cracks or warping. While the intake is off you might as well pull the exhaust manifold for inspection.

Inspect the oil to see if there are any signs of coolant. Head gasket, cracked head, block are all possible given the overheating scenario.

 

Oooh. I had forgotten all the implications of an over heated engine... Even the tough 300. I've been losing antifreeze on a regular basis, cant keep the radiator full. I can keep it at 4/5ths full and it won't lose any. My last oil change never showed any in the oil. which is due again anyway, so I'll check it. Radiator had sprung a leak after rear ending a Cadillac (it won), though THAT issue only bent the crush point on the frame and my bumper. I did replace my top radiator hose mount and thermostat last year. I had thought about a head gasket, but couldn't be sure. And I had noticed my engine oil leaks a little, which it never did before.

Anyway at the time, my mechanic had said "If it's not leaking something it's not running."

 

Finally got the manfold off the other day. Should have just pulled the engine. so when I set a straight edge on the manifold, the most daylight I can get is .014 Is that too much for a gasket to take care of or should I send it to a machinist? I did a compression test and they are all good, the highest difference I got (161-175psi range) is 14 psi. Cleaned the injectors and they are Aok as well, good spray, clean and the selenoid valve works fine.

And when I had overheated the engine, that was early last summer. I drove 8k miles without any issues till recent.

 

You could try using a good gasket to see if it will seal or to be assured have that exhaust manifold machined. Look very close for signs of cracking.